The present invention relates generally to a zoom lens, and specifically to a zoom lens that has a half angle of view of about 35° to about 45° at the wide-angle end and is adapted to cover a standard angle-of-view area having a zoom ratio of about 2.5 to about 4.
More specifically, the present invention concerns a zoom lens suitable for use as an interchangeable lens for single-lens reflex cameras.
Downsizing-oriented, simple zoom lens arrangements have been proposed so far in the art. For instance, Patent Publication 1 discloses a zoom lens comprising, in order from its object side, a first lens group of positive refracting power, a second lens group of negative refracting power and a third lens group of positive refracting power, with each group moving for zooming. It is said therein that the zoom lens is easy to carry and cuts back on fabrication cost due to a simplified lens mount arrangement and a short length at the wide-angle end.
A problem with the zoom lens set forth in Patent Publication 1 is, however, that for the reason that the second lens group is made up of two lenses, it is difficult to maintain optical properties, and there is not bound to be enough of brightness. With the zoom lens exemplified in Example 2 of Patent Publication 1, astigmatism is likely to occur at or near an intermediate focal length, although the second lens group is made up of three lenses. Nowhere in Patent publication is there anything about focusing operation.
Patent Publication 1
JP(A)4-321007